Process for the manufacture of wall plugs



Jan. 19, 1943. w s 2,308,825

PROCESS FOR THE MANUFACTURE OF WALLYPLUGS awue/rvtom Filed Aug. 2, 1940Shauna/1 Patented Jan. 19, 1943 PROCESS FOR THE MANUFACTURE OF WALLPLUGS John Joseph Rawlings, London, England, assignor to The RawlplugCompany Limited, London,

England Application August 2, 1940, Serial No. 349,524 In theNetherlands August 19, 1939 '7 Claims.

This invention relates to improvements in wall plugs of the kindintended to be inserted in prepared holes in walls or the like in orderto provide a secure fastening for screws, nails and like fasteningdevices, and further relates to improvements in the manufacture of suchplugs.

Wall plugs are already known comprising strands of fibrous materialarranged longitudinally to form a tube, and held in the tubular form bymeans of an adhesive. Tubular wall plugs are also already known whereinthin metal wires are combined with fibrous strands, and are woven orplaited into a tubular form, e. g., around a mandrel; such woven orplaited fibrous plugs, with or without the inclusion therein of wires,have been impregnated with various media, such as glue or other suitableadhesive, sodium silicate, or artificial resin.

In such known plugs, the impregnation of the plug has always beenobtained either by passing the separate strands of fibre through a bathof the impregnating medium before formation into a plug or by passingthe already formed plug through a bath of impregnating medium.

According to the present invention, a tubular wall plug is providedhaving an inner layer formed either of strands arranged longitudinallyside by side, or by a strip of thin metal bent longitudinally to form atube, and having an outer layer formed of strands which are woven orplaited together, the two tubular layers of strands being held togetherby means of an adhesive or the like with which all the strands in bothlayers of the plug are impregnated.

Each tubular layer may comprise only strands of fibrous material, butpreferably the outer layer comprises thin metal wires combined with someor all of the woven or plaited fibrous strands. If desired wires mayalso be incorporated with the inner layer when such layer compriseslongitudinally arranged fibrous strands.

The wires may be incorporated with the outer layer of woven or plaitedfibrous strands by being woven or plaited therewith or by being twistedaround the separate fibrous strands before weaving or plaiting or may bepresent in such separate fibrous strands before weaving or plaiting inthe form of cores. Similarly, where wires are provided in combinationwith longitudinal fibrous strands to form the inner layer of the plug,they may either be twisted around some or all of the separate strands ormay form cores to some or all of such strands.

In the formation of wall plugs in which thin metal Wires, e. g.,. copperwires, are incorporated,

difiiculties have arisen in the withdrawal of the tubular structure fromthe mandrel on which it is formed, before it is out into lengths, andfurther disadvantages have been encountered when it has been proposed toavoid the use of a mandrel in that when the tubular structure,unsupported by any mandrel, is impregnated and thereafter dried andhardened, distortion of the tube often results and it is difiicult orimpossible to obtain a dried tubular structure of a true circular shapein cross section or with any accuracy to obtain a tubular structure ofgiven definite internal and external diameters.

The disadvantages and difficulties above mentioned are obviated in themanufacture of wall plugs according to the present invention.

In the manufacture of the improved wall plugs in accordance with theinvention, the woven or plaited strands. comprising the outer layer ofthe plug are led in a braiding machine from the usual separate spools orbobbins to the point where they are plaited one over the other, theinner layer of the plug being fed inwardly of the separate strands sothat the braiding or plaiting takes place actually around the innertubular layer. The braiding or plaiting is completed within a closedchamber to which the impregnating medium is fed under a constantpressure.

Thus the impregnating medium is forced into contact with the strands offibre comprised in the outer layer of the plug at a time when suchstrands are still separate, i. e., just before they are braided orplaited together, with the result that a complete impregnation into thecomponent fibres of each separate strand of fibre takes place. Sincethe. impregnating media commonly employed in the manufacture of wall.plugs are ordinarily of a relatively thick and viscous nature, it isobvious that complete impregnation through the fibres form-ing each ofthe strands cannot be obtained by passing an already plaited tubularstructure through a bath of impregnating medium even if the medium isunder pressure in such bath. The new process of manufacture accord.- ingto this invention thus provides a considerable advance in respect of thestep of impregnation. The other prior known method of impregnation, i.e., that of impregnating the separate strands before they reach thebraiding or plaiting point, obviously results in the loss ofimpregnating medium, accumulation of partially dried and hardenedimpregnating medium at the point of braiding (which causes frequentstoppages of the machine for removal thereof) and difiiculty in drawingthe impregnated strands through the or without the incorporation ofmetal wires, the

said inner layer may be formed in the known manner upon a mandreklwhichextends inwardly through the braiding machine, the outer layer ofstrands being braided or plaited around the inner layer while the latteris upon the mandrel,

It has been found that the presence upon the mandrel of this inner layerof longitudinally arranged strands of fibrou material overcomes thediificulty which is usually experienced in attempting to withdraw aWoven or plaited tubular structure from a mandrel owing to the fact thatany longitudinal tension applied to a woven or plaited tubular structureresults in an increase in the length of the tube and a contraction inits diameter which causes the tube to grip and hold the mandrel. Thepresence between the mandrel and the plaited or woven tube of the innerlayer of longitudinally arranged strands prevents such gripping of themandrel.

When the inner layer of the improved plug is formed of a strip ofsheetmetal of suitable thickness bent to form a tube or cylinder, the saidtube or cylinder serves. adequately to maintain to form a tubularstructure 5, shown partly in section in Figure 1.

An impregnating medium of the kind previously mentioned isfed into thechamber 4 under pressure from a supply pipe or conduit 6; it will beseen from the drawing that the separate strands 3 of fibre comprisingthe outer layer of the plug, with or without wires incombination withsuch strands, are substantially each surrounded by the impregnatingmediumv in the chamber 4, thus ensuring complete impregnation Qof eachstrand just before and also during the time in which it is plaited withthe other strands to form the tubular structure 5, by reason of the thecomposite plug in its true cylindrical shape,

andno mandrel is thus necessary. The inner layer may be formed byleading a strip of sheet metal inwardly towards the chamber in which theouter fibrous strands are braided in an impregnating medium, the saidstrip passing into this chamber through a collar or die through which itis pulled by any convenient means and by which it is bent and shapedinto a tube or cylinder.

In the accompanying drawing,

Figure 1 is a diagrammatic view illustrating the characteristic elementsof apparatus for carrying out the process accordingto the invention,applied to the production of a plug having an outerlayer of fibrousstrands woven together with or without metal wires, and an inner layerof fibrous strands with or without metal wires, such strands extendinglongitudinally of the plug Figure 2 is a diagrammatic view illustratingin plan the formation of a wall plug by the apparatus shown in Figure 1,V V

Figure 3 is a view similar to Figure 1, wherein the inner layer of theplug is formed by a thin metalistrip bent to the shape of a tube or cylinder. 7 Figures 4 and 5, respectively, are diagrammaticviewsillustrating the construction of the finished wall plugs produced by theapparatus shown in Figures 1 and 3.

As shown in the drawing, Figures 1 and 2, the improved wall plug maycomprise an inner layer formed of longitudinally arranged strands 2 offibrous material of any suitable kind, e. g., of jute, disposed side byside upon 'a cylindrical mandrel I. If desired, the strands 2 may havemetal wires, e. g., thin copper wires, combined therewith, either ascores or twisted around some or allof the individual strands.

The outer layer of the plug is formed by strands ,3,.which may be offibre alone, but preferably some or all of the strands 3 are combinedwith thin metal wires. The strands 3 are led in a pressure under whichthe impregnating medium is supplied.

It is to be understood that the drawing is diagrammaticonly, in orderthat the invention may be readily and clearly understood, and that forthis purpose the dimensions of the strands 3 have been reduced and thesize of the entry aperture in the chamber 4 ,ha been exaggerated for thesake of, clarity. It WilI-beappreciated that in this apparatus, asshownin Figures '1 and 3, the aperture through which the separate outerstrands 3 and the inner strands 2 or the tube 8' are fed into theimpregnation pressure chamber t is considerably smaller than isindicated in the drawing, and is of such dimensions as to besubstantially completely filled or occluded by the inward passageof thefibrous strands, in

. order to prevent the escape of impregnating mestant pressure in thechamber 4.

braiding machine of a known kind to a chamber dium through suchaperture. In practice, the,

pressure of the impregnating medium in the pres! sure chamber 4 isregulated inrelation to the speed at which thefibrous strands pass intoand out of the chamber 4, and is such a speed that the rate of supply ofimpregnating medium through the pipe 6 is equal to the rate ofadsorption thereof into the fibrous strands, thus maintaining a con- InFigure 3 of the drawing, the strands 2 of Figure 1 are replaced by atube 8 formed by bending a strip 1 of thin sheet metal. Suitable formingor=shaping means are provided as at 9,

' whereby the fiat strip 1 is formed into the tube 8.

As shown in Figures land 3, the improved plug passes directly from thechamber'4, in which braiding of the fibrousstrands 3" of the outer layerof the plug is completed and in whichimpregnation of the strands 3 andalsoof the strands 2 takes place, into a shaping and sizing die H],which is preferably. heated, wherebyla-rod or tube of wall plugisformedof therequired accurate dimensions and of .a true cylindrical shape, andwherebythe impregnating medium is dried and hardened A plurality ofsuchsizing dies may be provided to reducethe diameterof the plug, ifdesired, so that accurate meansmay be available for the continuousproduction-from one machine of plugs'of differing diameters..--

After passing through the sizing dies,-suitable means of anysuitablekind are provided for cut-' ting off the desired .lengthsof-plug,

I claim: i

1. A process for the braiding together the fibrous strandsiand the m talwires into a ubu rstructure in said cham anufacture of wall plugs.comprising feeding ap stripof sheet metalto'a shaping die whereby it isbent to form atube; leading a plurality of fibrous strands and aplurality of thin-metal wires to aisubstantially closed chamber, drawingthe sheet metal tube through such chamber, maintaining a supply ofimpreg' nating fluid under pressure in such: chamber,

her around the sheet metal tube, drawing a continuous length of thecomposite tube thus formed from the said chamber, drying such tube byheating, and cutting it into suitable lengths.

2. A process for the manufacture of tubular wall plugs, comprisingleadin a plurality of fibrous strands and a plurality of thin metalwires to a substantially closed chamber, maintaining a supply ofimpregnating fluid in such chamber, braiding together the fibrousstrands with the metal wires into a tubular structure in such chamber,applying pressure to the impregnating fluid in such chamber, drawing acontinuous length of impregnated tube from such chamber, drying theimpregnated tube and cutting it into suitable lengths.

3. A process for the manufacture of tubular wall plugs, comprisingleading a plurality of fibrous strands and a plurality of thin metalwires to a substantially closed chamber, maintaining a supply ofimpregnating fluid in such chamber, braiding together the fibrousstrands with the metal wires into a tubular structure in such chamberaround a mandrel passing through such chamber, applying pressure to theimpregnating fluid in such chamber, drawing a continuous length ofimpregnated tube from such chamber, drying the impregnated tube andcutting it into suitable lengths.

4. A process for the manufacture of tubular wall plugs, comprisingleading a plurality of fibrous strands and a plurality of thin metalwires to a substantially closed chamber, maintaining a supply ofimpregnating fluid under pressure in such chamber, braiding together thefibrous strands with the metal wires into a tubular structure in suchchamber around a mandrel passing through such chamber, drawing acontinuous length of impregnated tube from such chamber through a sizingand shaping die, drying the impregnated tube and cutting it intosuitable lengths.

5. A process for the manufacture of tubular wall plugs, comprisingarranging a plurality of fibrous strands longitudinally around acylindrical mandrel, such mandrel together with the fibrous strandsarranged around it extending through a substantially closed chamber,leading into said chamber a plurality of separate fibrous strands and aplurality of separate metal Wires, maintaining a supply of heatedimpregnating fluid in said chamber, braiding together in said chambersaid separate fibrous strands and said separate metal Wires to form atubular structure around the fibrous strands arranged longitudinallyaround said mandrel, withdrawing the composite layered tubular structurefrom the mandrel, and cutting it into suitable lengths.

6. A process for the manufacture of tubular wall plugs, comprisingleading a plurality of fibrous strands and a plurality of thin metalwires to a substantially closed chamber, maintaim'ng a supply ofimpregnating fluid in such chamber, maintaining the said fluid under aconstant pressure in such chamber, braidin together the fibrous strandswith the metal wires into a tubular structure in such chamber, drawing acontinuous length of impregnated tube from such chamber, drying theimpregnated tube and cutting it into suitable lengths.

7. A process for the manufacture of tubular Wall plugs, comprisingleading a plurality of fibrous strands and a plurality of thin metalwires to a substantially closed chamber, maintaining a supply ofimpregnating fluid within such chamber, braiding together the fibrousstrands with the metal wires into a tubular structure Within suchchamber, app-lying pressure to the impregnating fluid in such chamber,drawing a continuous length of impregnated tube from such chamberthrough a heated sizing die, and cutting the dried and sized tube intosuitable lengths.

J. J. RAWLINGS.

